The present invention is generally related to medical devices. More specifically, the present invention is related to intravascular catheters having improved tips and guide wire lumens. The present invention includes catheters having an inflatable bulbous tip, a tip pre-stressed to expand outward, an expandable tip, and an inner-most guide wire tube disposed within an inner guide wire tube.
Intravascular diseases are commonly treated by relatively non-invasive catheter-based techniques such as percutaneous transluminal angioplasty (PTA) and percutaneous transluminal coronary angioplasty (PTCA). Catheter-based treatment and diagnostic techniques can also include atherectomy, laser radiation, ultrasonic imaging along with others. These therapeutic techniques are well known in the art and typically involve the use of a catheter, such as a balloon catheter or catheter having some other therapeutic device located proximate a distal end of the catheter, with a guide wire, possibly in combination with other intravascular devices. A typical balloon catheter has an elongate shaft with a balloon attached proximate the distal end and a manifold attached to the proximal end. In use, a balloon catheter is advanced over a guide wire such that the balloon is positioned adjacent a restriction in a diseased vessel. The balloon is then inflated and the restriction in the vessel is opened.
A more recent technique for treating intravascular diseases includes the use of a balloon dilatation catheter to carry and place a stent within the lumen of the blood vessel at a stenosed area. The stent is a generally cylindrical body with a lumen therethrough which is balloon-expanded when placed at the site of a lesion from a compressed configuration to an expanded configuration which physically prevents the blood vessel lumen from blocking over the length of the stent. The wall of the stent is preferably made from a metallic material and includes a pattern of interconnected struts with interstitial spaces therebetween which are open through the cylindrical wall. Stents of this design are disclosed in U.S. Pat. No. 5,449,373, and in PCT publication WO 96/03092, the disclosures of which are incorporated herein by reference. Catheters specifically designed to deliver such stents are disclosed in U.S. Pat. No. 4,950,227, the disclosure of which is also incorporated herein by reference.
There are two basic types of balloon catheters used in combination with a guide wire, namely, over-the-wire (OTW) catheters and single-operator-exchange (SOE) catheters. The construction and use of both OTW catheters and SOE catheters are well-known in the art. An example of an OTW catheter may be found in commonly-assigned U.S. Pat. No. 5,047,045 to Arney et al., the disclosure of which is incorporated herein by reference. An example of an SOE balloon catheter is disclosed in commonly-assigned U.S. Pat. No. 5,156,594 to Keith, the disclosure of which is incorporated herein by reference.
PTA and PTCA catheters are preferably designed to optimize pushability, trackability and crossability. Pushability is defined as the ability to transmit force from the proximal end of the catheter to the distal end of the catheter. Trackability is defined as the ability to navigate tortuous vasculature. Crossability is defined as the ability to navigate the balloon catheter across narrow restrictions in the vasculature.
The trackability of a particular catheter design is analyzed in terms of the trackability of the distal portion of the catheter, as this portion must track the guide wire through small tortuous vessels to reach the stenosed area to be treated. A more flexible distal portion has been found to improve trackability. Further, in transitioning from a stiff proximal segment or portion of the catheter shaft to a more flexible distal portion of the catheter shaft, it has been found that kinking readily occurs at the joint between the two shaft segments of differing flexibility. The increased flexibility of the distal section also makes this portion of the catheter less able to be pushed from the proximal end of the catheter.
The crossability is related to the trackability of a particular catheter design in that crossability is affected by the flexibility of the distal section of the catheter. Further, however, the crossability of the catheter in the area of a tight lesion is effected by the design of the distal tip of the catheter. The distal tip includes that region distal of the balloon which tracks the guide wire and at the distal-most portion that portion which first must pass through a stenosed area. Thus, much effort has gone into designing tips with improved crossability such as those disclosed in co-pending application Ser. No. 08/950,864, filed on Oct. 15, 1997 and entitled xe2x80x9cOVER-THE-WIRE CATHETER WITH IMPROVED TRACKABILITYxe2x80x9d, the disclosure of which is incorporated herein by reference.
Although the above-referenced tip designs improve trackability and crossability, it has been found that these tip designs can be detrimental to the procedures utilized in placing and expanding a stent. More specifically, in the initial placement of a stent, the stent is preloaded over the deflated balloon and the improved tip designs actually help in getting the stent in place across a lesion because the tip provides a leading edge through the lesion. However, it is common procedure to then expand the stent by inflating the balloon followed by deflation of the balloon. The balloon catheter is then pulled back a distance over the guide wire and the placement of the stent evaluated under fluoroscopy. It is many times necessary to again move the balloon distally across the stent to perform a post or subsequent inflation of the balloon within the stent to properly seat the stent against the vessel wall. In these instances, the balloon catheter must be moved distally over the guide wire to position the balloon across the stent. In these situations, the tip must first pass through the interior of the stent. It has been found that tips incorporating designs which improve the crossability of the balloon catheter over a lesion can get caught on the struts of the stent when passing therethrough and make it difficult to post dilate the stent. This is particularly true in a bend where the leading edge of the tip catches the outside wall of the curve because the guide wire tends to be pressed against the outside radius of the curve while the distal-most tip of the catheter is biased that same direction as it attempts to follow the curve.
The above described problems associated with tip designs which are optimal for crossability of a lesion, but detrimental to crossing a stent are also prevalent in subsequent treatment of lesions that are distal of a stent within the same artery. To dilate a more distal lesion, the balloon dilatation catheter to be utilized must first pass through the lumen of a stent if one had been previously placed in the artery. The same problems with the tip catching on struts can occur.
Therefore, there is an unmet need for a catheter design which incorporates a tip which is designed for crossing lesions but which is also capable of being converted or modified to a second configuration which is suitable for crossing through the interior lumen of a stent without getting caught on a strut. The present invention, provides such a tip design or tip design in combination with a guide wire design which includes means for reconfiguring the distal-most portion of a catheter to prevent strut and tip interaction which is detrimental to crossing through the lumen of the stent.
The present invention is directed to a catheter assembly having a therapeutic device mounted proximate a distal end thereof for intravascular treatment of the vessel at a location in the lumen therein. A preferred embodiment includes an over-the-wire balloon catheter, which is described in detail herein, however, the balloon dilatation catheter can include any known type of balloon catheter including a fixed wire catheter or a single operator exchange catheter. Further, the therapeutic device mounted proximate the distal end of the catheter disclosed herein is an inflatable balloon, however, any other known therapeutic device can be mounted on the catheter and embody the invention disclosed herein.
The over-the-wire balloon dilatation catheter generally includes an elongate tubular member having a proximal end and a distal end with a guide wire receiving lumen extending therethrough. The elongate tubular member is coaxially disposed within an outer tubular member which also extends over a portion of the inner tubular member over a portion of its length. The inner tubular member extends distally beyond the outer tubular member, and an inflation lumen is formed in the annular space between the two tubular members. A balloon having a proximal end and a distal end is mounted proximate the distal end of the catheter and forms an internal volume therein in fluid communication with the inflation lumen. In preferred embodiments, the proximal end of the balloon is sealingly mounted proximate the distal end of the outer tubular member and extends distally to a distal end which is sealingly connected to the outside of the inner tubular member which extends beyond the outer tubular member. The proximal end of the catheter includes a hub assembly which provides a guide wire receiving port which goes into the lumen of the inner elongate tubular member and an inflation port which is in fluid communication with the annular inflation lumen.
The catheter includes a tip portion which, in preferred embodiments, is that portion of the catheter distal of the balloon and is generally formed by a portion of the inner tubular member having the guide wire lumen extending therethrough. The tip is designed to initially be optimum for aiding the catheter in tracking the guide wire and assisting in crossing a lesion to be dilated. Thus, the flexibility and shape of the tip are modified to aid in crossing. For example, the tip may be necked down relative to the proximal diameter of the inner or may be conically shaped having a decreasing outside diameter distally to readily penetrate an obstructed vessel.
The various embodiments of the present invention are directed to tip designs and tip and guide wire designs which, in a first configuration, are optimal for crossing a lesion. A tip or tip and guide wire combination in a second configuration is optimal for crossing a placed stent in that the tip portion does not catch on the struts in a stent, particularly a stent placed in a bend of a vessel.
In a first series of embodiments, the tip assembly includes means for reconfiguring the catheter tip from a first configuration for crossing an obstruction in the vessel lumen to a second configuration for crossing a placed stent. One embodiment includes a severable distal tip section, which is removed after treating the obstruction, but leaves a proximal portion of the tip which is more suited for crossing a stent. The remaining portion of the tip may be more bulbous in cross section or have a larger lumen that is used in conjunction with a larger guide wire.
In an alternative embodiment, the distal-most tip can be reconfigured by rolling the distal-most portion back onto the inner tubular member so that in a first configuration the tip may be passed through a lesion or obstruction, but in the second configuration, the folded back portion forms a more bulbous tip which will not catch on a strut as readily. Alternatively, the tip portion may be changeable from a straight configuration to a bent configuration which aids in crossing the stent when in a bent configuration.
In another embodiment, the inner tubular member may be slidable within the catheter or a sheath may be utilized which, when extended, provides a tip which readily crosses a lesion, but when retracted, the remaining tip portion is more bulbous or blunt for reducing the likelihood that this tip catches on the strut of a stent.
Finally, the tip of the catheter may include a distal-most portion which is rotatably secured to the inner tubular member and extends distal of the balloon. The inside lumen of the rotatably secured tip can include at least one helical protrusion on the lumen of the tip. When the catheter is moved relative to the guide wire therethrough, friction between the helical protrusion and the guide wire rotates the tip which decreases the likelihood that such tip will become caught on a strut of a stent.
In a second series of embodiments, the configuration of the guide wire utilized in conjunction with the catheter tip assembly is shaped to prevent the distal tip of the catheter from catching on the stent strut when the guide wire is selectively positioned relative to the tip, wherein it deflects or pulls the tip away from the strut while maintaining the guide wire in contact with the stent. This can include designing the guide wire with a preshaped bend at a select location, or with one or more helical coils which would be positioned within the inner lumen of the stent as the catheter crossed the stent. Alternatively, the guide wire can include a bulbous portion which, in a retracted portion, provides a more bulbous cross section on the distal tip to prevent the catheter tip from catching on a stent strut.
In another alternative embodiment, the guide wire can be caused to vibrate from the proximal end of the catheter so that the portion of the guide wire distal of the balloon vibrates in a preselected pattern which assists in preventing or deflecting a catheter tip which may get caught on a stent strut.
The distal tip of the catheter may be designed with an inflatable cuff surrounding a distal portion of the tip. The cuff can be in fluid communication with the guide wire lumen through a hole in the wall of the tip. Fluid may be injected down the guide wire lumen with sufficient pressure drop across the guide wire through the tip so that a portion of the inflation fluid fills the cuff and creates a more bulbous overall tip profile that would be less likely to catch on a stent strut when passing through the lumen of the stent.
The present invention can include a balloon catheter having a first balloon and a second, distal inflatable balloon or cuff disposed distal of the first balloon. The second, distal balloon can be inflated to increase the cross-sectional profile or maximum radial extent of the distal-most region. Increasing the profile of the distal-most region can act to deflect the distal-most end away from a stent interior wall or end. In one embodiment, the first balloon interior is in fluid communication with the distal balloon interior. These embodiments have the advantage of not requiring a separate inflation lumen for the distal balloon, which could otherwise require a tube or lumen extending the entire length of the catheter.
In one embodiment, a one-way valve is disposed between the first balloon and the distal balloon, acting to prevent rapid deflation of the distal balloon. In this embodiment, inflating the first balloon can also inflate the second balloon, whereupon the first balloon can be deflated, leaving the distal balloon still inflated. In another embodiment, a controllable valve is disposed in the fluid space between the first balloon and the distal balloon. The controllable valve can be opened, thereby allowing fluid to flow from the first balloon into the distal balloon. Fluid flow between the distal balloon and the first balloon can be prevented by manipulation of the same valve. One valve is switchable between a first, open position, and a second, closed position. Another valve is biased to remain in a closed position, and can be manipulated via a pull wire to remain in the open position while the pull wire is retracted. In this embodiment, releasing the pull wire allows the valve to return to its closed state.
One balloon catheter incorporating the present invention includes a distal region including a tube having walls and a lumen therethrough. The tube has a plurality of slits through the walls and is formed of a pre-stressed material, which has a first configuration having a first cross-sectional profile or maximum radial extent and a second configuration having a greater cross-sectional profile or maximum radial extent. The tube is pre-stressed so as to attain the second configuration after insertion within the body. One preferred distal region is formed of a shape memory material such as Nitinol or a shape memory polymer which, upon attaining body temperature, expands the maximum radial extent of the distal region. One catheter has a distal region including flaps disposed within longitudinal slits, with the flaps curling outward when heated by warm body fluid. One catheter has a distal-most end having slits which terminate prior to the distal end. In this embodiment, the distal-most end can be cut by the treating physician, thereby exposing the longitudinal slits and allowing the tip to expand upon exposure to warm body fluids.
One catheter, according to the present invention, includes a distal region having an inner tube and an innermost tube slidably disposed within the inner tube. The innermost tube can be affixed to the inner tube at the distal-most end. In this embodiment, the distal region has a plurality of longitudinal slits defining flaps therebetween. The innermost tube can be retracted proximally, thereby pulling the distal-most end of the innermost tube and the inner tube disposed about the innermost tube. In response thereto, the flaps disposed between the longitudinal slits bulge outward, thereby creating a greater maximum radial extent or cross-sectional profile of the distal region. The outwardly protruding distal region flaps can act to deflect the distal-most end of the catheter away from stent walls and ends.
In another embodiment of the invention, a balloon catheter is provided having a first, inner guide wire tube having a first guide wire lumen therethrough. The catheter can include a manifold having a proximal tapered region disposed within. A second, smaller, inner tube having a second, smaller guide wire lumen can also be provided. The second guide wire tube can have a proximal adapter having a taper adapted to be slidably received within the proximal region of the balloon catheter manifold. The inner tube assembly thus provided can be disposed within the first guide wire tube and manifold, thereby providing a smaller guide wire lumen. In use, the balloon catheter can be used in conjunction with a first guide wire, where a first, larger guide wire is desirable. When use of a second, smaller guide wire is desired, the first guide wire can be retracted. The inner tube assembly can then be advanced through the catheter, with the second inner tube being thus disposed within the first inner tube. With the second inner tube thus disposed, a second, smaller guide wire can be advanced through th e second inner tube and through the distal end of the balloon catheter. The second, smaller inner tube can provide improved support for the smaller guide wire and can provide improved resistance against buckling. In one embodiment, the second, smaller inner tube has a length sufficient to extend distally from the distal end of the first, surrounding tube when the second tube is fully advanced within the first tube.